The purpose of this study is to evaluate the utility of claims data as a data source to evaluate quality of care in new onset rheumatoid arthritis; to measure the quality of care for patients with new onset rheumatoid arthritis with regard to arthritis co-morbid conditions and health care maintenance, and to identify factors associated with better attainment of quality standards. This study will prospectively follow a cohort of 400 patients with new onset rheumatoid arthritis for two years through patient surveys and claims data. Subjects will be enrolled through one large managed care organization (MCO) located in Southern California which represents an average of 2.8 million covered lives per year. Using a claims based algorithm, the 1998 through 1999 claims data for this MCO will be screened for incident cases of rheumatoid arthritis. Patients between ages 18 and 62 will be eligible for enrollment. A screening survey which will ascertain 1) whether a patient has been diagnosed with rheumatoid arthritis and/or 2) if the patient meets the 1987 American Rheumatism Association (ARA) criteria for rheumatoid arthritis by self report will be sent by mail to all eligible patients to invite participation. The first 400 responding patients who have had a prior diagnosis or meet the ARA criteria will be enrolled. Patients will complete telephone surveys which assess health status every six during the study. By using data elements from claims data, patient self report. and medical records, the structure, process, outcomes and quality of care will be assessed. Items measured in the claims data will be validated through the patient self report and medical record review. This study will inform us regarding the predictive value of claims data for identifying patients with rheumatoid arthritis and describing utilization. It will also describe the utility of claims data for assessing the process and quality of care for rheumatoid arthritis.